1. Field of the Invention
This specification relates to a method and a device for determining calibration parameters of a camera. Moreover, the specification relates to a method of controlling calibration parameters of a camera, to a computer program product and a computer readable storage medium. In addition, the specification relates to a camera comprising such a device.
2. Discussion of the Related Art
Recently, driving-assistance systems have been developed that comprise a camera which monitors the motion of the vehicle as well as the surroundings thereof. For example, these cameras may take images of the neighboring lane so as to detect neighboring vehicles and to alert the driver of the subject vehicle if he desires to change the lane, for example. In order to obtain a precise monitoring, camera calibration is an essential issue. Generally speaking, the camera calibration establishes the relationship between the 3D environment and its projection onto the image plane. The extrinsic parameters of a specific camera describe the relative position and orientation of the camera with respect to the world coordinate system. For example, the extrinsic parameters may be found through the extrinsic calibration. In addition, the intrinsic parameters of the camera model the projection of points from the camera coordinate system onto the image plane. For example, the intrinsic parameters comprise focal length, optical center etc.
Conventionally, camera calibration has been performed using known calibration objects. For example, after assembly of the vehicle or during an inspection such a calibration is performed with the camera using known calibration objects. Accordingly, the calibration parameters are estimated offline and used statically as initial values by the system. Generally, the intrinsic parameters of the camera are static. However, the extrinsic parameters can change slightly during use, e.g. caused by mechanical influences. However, wrong extrinsic calibration information will have a critical effect on the performance of the complete system. Accordingly, an automatic or self-calibration of the extrinsic parameters during runtime is desired. Therefore, a need exists for developing a method and a device of determining extrinsic calibration parameters of a camera.
US 2009/0290032 relates to a self calibration of extrinsic camera parameters for a vehicle camera.
It is an object of the present invention to provide an improved method and an improved device for determining calibration parameters of a camera. The above objects are solved by the claimed matter according to the independent claims.
The accompanying drawings are included to provide a further understanding of embodiments of the invention and are incorporated in and constitute a part of this specification. The drawings illustrate the embodiments of the present invention and together with the description serve to explain the principles. Other embodiments of the invention and many of the intended advantages will be readily appreciated, as they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale relative to each other. Like reference numbers designate corresponding similar parts.